Touch detection device, touch panel device, and calibration method for touch detection device

Abstract

To provide "a touch detection device, a touch panel device, and a calibration method of the touch detection device" for executing calibration in a situation where execution is appropriate.SOLUTION: The calibration controller 125 regards the detected capacitances Cn of the respective electrodes as the parasitic capacitances Cp of the respective electrodes, and calibrates the respective detection circuits 1211 of the sense block 121 so as to detect the capacitances Cn of the respective electrodes around the parasitic capacitances Cp of the electrodes in a case where the sum of the amounts of change in the parasitic capacitances Cp of the respective electrodes is larger than the predetermined threshold Th1 and the variation indication value that indicates the magnitude of variation in the parasitic capacitances Cp of the respective electrodes is smaller than the predetermined threshold Th2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for calibrating a touch detection device that detects a touch on a capacitive touch panel. [Background technology]

[0002] As a technique for calibrating a touch detection device that detects the amount of change in capacitance at each point on a capacitance-type touch panel, there is known a technique for calibrating the touch detection device so that the amount of change in capacitance can be detected in the same way for each coordinate, regardless of differences in base capacitance (the parasitic capacitance of each electrode in the case of a self-capacitance type, or the mutual capacitance of the Y electrode and X electrode when not touched in the case of a mutual capacitance type), which is the capacitance that serves as the reference for detecting the amount of change in capacitance due to touch (for example, Patent Document 1).

[0003] Also, a technique is known in which the calibration of a touch detection device is performed every time the device is started up (powered on) (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-141556 [Patent Document 2] International Publication No. 2017 / 158907 Summary of the Invention [Problem to be solved by the invention]

[0005] It is a heavy burden to perform the above-described calibration of the touch detection device every time it is started up, and it is redundant to perform the calibration until the base capacitance has not changed to such an extent that the amount of change in the capacitance cannot be detected correctly. Therefore, it is conceivable to widen the measurement range for detecting capacitance so as to encompass the expected range of change in capacitance, and to investigate, at startup or the like, whether the base capacitance has changed to such an extent that the range of change in capacitance is expected to deviate from the current measurement range, and only if a change has occurred, to calibrate the touch detection device to reset the measurement range.

[0006] However, in this case, the touch detection device is calibrated even when the base capacitance of a part of the touch panel changes significantly due to, for example, the temporary placement of a conductive object near the touch panel, but in this case, it is assumed that the conductive object will be removed after that, so it is not necessarily appropriate to perform calibration. That is, if calibration is performed in such a case, for example, it may not be possible to correctly detect the amount of change in capacitance after the conductive object is removed.

[0007] Therefore, an object of the present invention is to perform calibration of a touch detection device that detects the amount of change in capacitance at each point on a capacitive touch panel only under circumstances in which performing calibration is truly appropriate. [Means for solving the problem]

[0008] To achieve the above object, the present invention provides a touch detection device used for detecting touches on a capacitive touch panel, comprising: a touch detection unit that detects the capacitance of each of a plurality of points on the touch panel, and a calibration unit that performs calibration to adjust the range in which the touch detection unit detects the capacitance for each point. Here, the calibration unit acquires the capacitances of the plurality of points detected by the touch detection unit at a predetermined trigger, and, if a change level representing a level of change in the capacitance of each acquired point from the capacitance at the time of the previous calibration is greater than a predetermined level and an index value representing the degree of variation in the capacitance of each acquired point is smaller than a predetermined value, performs calibration to adjust the range in which the touch detection unit detects the capacitance for each point to include both the capacitance of the point when touched and when untouched, based on the capacitance acquired for that point.

[0009] Here, the touch detection device may be configured such that the calibration unit uses, as the change level, the sum of the amounts of change in the capacitance at each point acquired from the capacitance at the time of the previous calibration. The touch detection device may be configured such that the calibration unit uses the difference between the maximum and minimum values ​​of the capacitance of each point obtained as the index value. Alternatively, in the calibration unit of the above touch detection device, the index value may be the difference between the maximum and minimum values ​​of the moving average of two or more points, with one direction on the touch panel as the movement direction, of the capacitance of each acquired point, or the index value may be the difference between the maximum and minimum values ​​of the average of each of a plurality of areas into which the touch panel is divided in at least one direction, of the capacitance of each acquired point.

[0010] In addition, in the above touch detection device, the calibration unit may adjust the range in which the touch detection unit detects the capacitance for each point to a range centered on the capacitance acquired for that point. Furthermore, the above touch detection device may be configured such that the calibration unit corrects the acquired capacitance of each point so that the design capacitance variation is at least partially offset, and a value representing the degree of variation in the corrected capacitance of each point is calculated as the index value.

[0011] Furthermore, the above touch detection device may be configured such that, after performing the calibration, the calibration unit acquires the capacitances of the plurality of points detected by the touch detection unit, and when an index value representing the degree of variation in capacitance of each acquired point is greater than the predetermined value, the range in which the touch detection unit detects the capacitance for each point is restored to the range before performing the calibration.

[0012] In the above touch detection device, the predetermined trigger is, for example, startup of the touch detection device. In addition, in the above touch detection device, the touch panel may be a self-capacitance touch panel including a plurality of X electrodes and a plurality of Y electrodes, and each of the X electrodes and each of the Y electrodes may be the points at which the touch detection unit detects capacitance. The present invention also provides a touch panel device including the above touch detection device and the capacitive or self-capacitive touch panel.

[0013] According to the touch detection device or touch panel device described above, the capacitance of multiple points detected by the touch detection unit is regarded as a base capacitance that serves as a reference for detecting the amount of change in capacitance due to touch at that point, and calibration is performed only when the level of change in the base capacitance of the multiple points relative to the base capacitance at the time of the previous calibration is large and the variation in the base capacitance of each point is small.

[0014] Therefore, calibration can be performed when the base capacitance has changed overall due to changes over time, etc., while preventing calibration from being performed when a conductive object is temporarily placed near the touch panel and the base capacitance has changed significantly locally. Therefore, calibration can be performed only under circumstances where it is truly appropriate to perform it. [Effects of the Invention]

[0015] As described above, according to the present invention, calibration of a touch detection device that detects the amount of change in capacitance at each point on a capacitive touch panel can be performed only under circumstances in which it is truly appropriate to perform calibration. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram showing a configuration of a touch panel unit according to a first embodiment of the present invention. [Figure 2] 2 is a diagram showing the configuration of electrodes of the touch panel according to the first embodiment of the present invention, and the relationship between the electrodes and detection circuits. FIG. [Figure 3] 1 is a diagram showing a configuration of a detection circuit according to a first embodiment of the present invention. [Figure 4] FIG. 3 is a diagram illustrating calibration of a detection circuit performed in the first embodiment of the present invention. [Figure 5] 1 shows an application example of the touch panel unit according to the first embodiment of the present invention. [Figure 6] 5 is a flowchart showing a calibration process according to the first embodiment of the present invention. [Figure 7] FIG. 3 is a diagram showing an example of a variation index value used in the first embodiment of the present invention. [Figure 8] 10A and 10B are diagrams illustrating a touch panel according to a second embodiment of the present invention and an example of correction of capacitance distribution. [Figure 9] 10 is a flowchart showing a calibration process according to a second embodiment of the present invention. [Figure 10]10 is a flowchart showing a calibration process according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described taking as an example an application to a self-capacitance touch panel. First, the first embodiment will be described. FIG. 1 shows the configuration of a touch panel unit according to the first embodiment. As shown in the figure, the touch panel unit 1 is a device that functions as a pointing device for the host device 2. The host device 2 also includes other peripheral devices 3 such as a display unit. The touch panel unit 1 includes a touch panel 11 and a touch detection device 12 . The touch detection device 12 includes a sense block 121, a scan control unit 122, a memory 123, a data processing unit 124, and a calibration controller 125. As shown in FIG. 2a, the touch panel 11 includes a structure in which an X electrode group in which X electrodes extending in the Y direction are aligned in the X direction as shown in FIG. 2b and a Y electrode group in which Y electrodes extending in the X direction are aligned in the Y direction as shown in FIG. 2c are stacked in an insulated manner, and the sense block 121 of the touch detection device 12 includes detection circuits 1211 provided in one-to-one correspondence with the Y electrodes and X electrodes and connected to the corresponding electrodes.

[0018] 2b and 2c, each of the X and Y electrodes has a parasitic capacitance with respect to ground, which will be denoted as Cp below. This parasitic capacitance Cp serves as the base capacitance that serves as the reference for detecting the amount of change in capacitance due to touch. Hereinafter, for the sake of convenience, when there is no need to distinguish between the X electrodes and the Y electrodes, both electrodes will be referred to generically as "electrodes." Next, FIG. 3 shows the configuration of the detection circuit 1211. As shown in the figure, the detection circuit 1211 includes a sequence controller 12111, a charging circuit 12112, a first switch 12113, a second switch 12114, a constant current circuit 12115, a third switch 12116, an attenuator 12117, a capacitor 12118, a fourth switch 12119, and a digitizer 121110.

[0019] In such a configuration, when a scan signal SCN is input from the scan control unit 122, the sequence controller 12111 causes the detection circuit 1211 to perform a series of operations consisting of the following first period operation, second period operation, and third period operation. That is, first, in the first period, only the first switch 12113 is turned on, the charging circuit 12112 is connected to the corresponding electrode, and the capacitance Cn between the corresponding electrode and ground is charged. This capacitance Cn is equal to the parasitic capacitance Cp of the corresponding electrode when no touch occurs, and when a touch occurs, it is the sum of the corresponding electrode parasitic capacitance Cp and the capacitance Ch between the corresponding electrode and ground via the human body.

[0020] Next, in the second period, the first switch 12113 and the fourth switch 12119 are turned off, and the second switch 12114 is turned on, so that the charge stored in the capacitance Cn of the corresponding electrode is transferred to the capacitor 12118 via the attenuator 12117. Also, during the second period, the third switch 12116 is turned on for the time t set by the calibration controller 125, so that a portion of the charge flowing from the capacitance Cn of the corresponding electrode is branched to ground.

[0021] Next, during the third period, only the fourth switch 12119 is turned on, and a voltage corresponding to the charge stored in the capacitor 12118 is applied to the digitizer 121110, which converts the applied voltage into a digital value and outputs it to the memory 123 as RAW data for storage.

[0022] As a result, the output of the digitizer 121110 is proportional to the capacitance Cn of the corresponding electrode. Now, in such operation, during the second period, the charge stored in the capacitor 12118, and therefore the voltage applied to the third digitizer, can be adjusted by turning on the third switch 12116 for a time t, to shift the measurement range, which is the range of electrode capacitances Cn that the digitizer 121110 can correctly convert into digital values.

[0023] Therefore, the detection circuit 1211 can be calibrated by having the calibration controller 125 send a signal t_SET to the sequence controller 12111 to set, for example, the time t for turning on the third switch 12116 so as to offset the change in the parasitic capacitance Cp of the corresponding electrode.

[0024] Returning to FIG. 1, scan control section 122 outputs the above-mentioned scan signal SCN sequentially to each detection circuit 1211 of sense block 121 at a timing synchronized with a synchronization signal input from data processing section . The data processing unit 124 analyzes the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211, calculates whether a touch has occurred, and if so, the XY coordinates at which the touch occurred, and outputs the results to the host device 2. In addition, when the touch panel unit 1 is started up (powered on), the calibration controller 125 executes a calibration control process using the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211, and performs calibration to reset the time t for turning on the third switch 12116 of each detection circuit 1211, if necessary.

[0025] First, calibration performed as needed in the calibration control process will be described. 4a, if the time t for turning on the third switch 12116 of the detection circuit 1211 is set so that the digitizer 121110 digitizes the electrode capacitance Cn of 1000 fF to 7000 fF into a digital value of −32768 to +32768, the measurement range MR of the electrode capacitance Cn will be 1000 fF to 7000 fF. In this case, all capacitances Cn less than 1000 fF, which are below the measurement range MR, will be digitized to −32768, and all capacitances Cn greater than 7000 fF, which are above the measurement range MR, will be digitized to +32768.

[0026] Therefore, if the parasitic capacitance Cp of the electrode is 4000 fF and the increase in the electrode capacitance Cn due to touch (capacitance Ch via the human body) is approximately 1000 fF, the electrode capacitance Cn before and after touch, as indicated by the arrow, falls within the measurement range MR, and the change in the electrode capacitance Cn can be detected without any problems. On the other hand, when this measurement range MR is set, if the parasitic capacitance Cp of the electrode changes to 7500 fF as shown in Figure 4b, both the electrode capacitance Cn before and after the touch as indicated by the arrows will fall outside the measurement range MR, and the change in the electrode capacitance Cn will no longer be detectable. Therefore, in calibration, for example, as shown in Figure 4c, the measurement range MR is reset by changing the time t for turning on the third switch 12116 of the detection circuit 1211 so that the parasitic capacitance Cp of the electrode is as close to the center value of the measurement range MR as possible. However, in the calibration, it is not necessary to reset the measurement range MR so that the parasitic capacitance Cp of the electrode is at the center value, and for example, as shown in Fig. 4d, the measurement range MR may be reset to another range in which both the capacitance Cn of the electrode before and after touch are expected to fall within the measurement range MR. In this case, the calibration controller 125 will set the time t for turning on the third switch 12116 in the sequence controller 12111 so as to partially cancel out the change in the parasitic capacitance Cp of the corresponding electrode.

[0027] Now, the calibration control process according to this first embodiment is applied when the touch panel 11 of the touch panel unit 1 is a touch panel 11 arranged on the surface of a display arranged on the center dashboard of a car, for example, as shown in FIG. 5a.

[0028] In the case of a display and touch panel 11 arranged as shown in Figure 5a, a user may non-permanently place a smartphone 4 connected to a charging cable in front of the display and touch panel 11 using a holder, as shown in Figure 5b. As shown in Figure 5c, which shows the distribution of the parasitic capacitance Cp of the electrodes in the X direction, distribution D1 is approximately flat when the smartphone 4 is not placed, whereas distribution D2 when the smartphone 4 is placed shows that the parasitic capacitance Cp is significantly larger in the area where the smartphone 4 is placed and its surrounding area.

[0029] In this case, when the detection circuit 1211 corresponding to each X electrode is calibrated based on the distribution D2 to set the measurement range MR, the measurement range MR of each detection circuit 1211 becomes as shown in the diagram MR'. Then, after performing such calibration, when the smartphone 4 is removed, the distribution of the electrode parasitic capacitance Cp returns to the distribution D1, so that in the X-direction range where the smartphone 4 is placed, the capacitance range around the parasitic capacitance Cp falls outside the measurement range MR, and it becomes impossible to detect changes in the electrode capacitance Cn.

[0030] Therefore, in the calibration control process, calibration is not performed in such cases, and the execution of calibration is controlled so that calibration is performed only under circumstances where the execution of calibration is truly appropriate. FIG. 6 shows the procedure for this calibration control process. Here, this calibration control process is performed by the calibration controller 125 when the touch panel unit 1 is started up (when the power is turned on). As shown in the figure, in the calibration control process, the calibration controller 125 first detects the parasitic capacitance Cp of the electrode corresponding to each detection circuit 1211 from the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211 (step 602).

[0031] In step 602, the parasitic capacitance Cp of each electrode is detected assuming that the capacitance Cn of the electrode represented by the RAW data is equal to the parasitic capacitance Cp. The capacitance Cn of the electrode can be determined, for example, by performing a reverse calculation on the RAW data, which applies the opposite action to the action of the detection circuit 1211, taking into account the time t at which the third switch 12116 is turned on.

[0032] Then, the amount of change in the parasitic capacitance Cp detected in step 602 from the value of the parasitic capacitance Cp detected in the previous calibration control process is calculated for each electrode, and it is checked whether the total amount of change calculated for each electrode is greater than a predetermined threshold value Th1 (step 604).If it is not greater, the calibration control process is terminated.

[0033] On the other hand, if the calculated total amount of change is greater than the threshold value Th1, a variation index value indicating the magnitude of variation in the detected parasitic capacitance Cp of the electrode is calculated, and it is checked whether the variation index value is greater than a predetermined threshold value Th2 (step 606).If it is greater, the calibration control process is terminated.

[0034] On the other hand, if the variation index value is not greater than the value Th2, the above-described calibration is performed for each detection circuit 1211 (step 608), and the calibration control process ends. According to this calibration control process, calibration is performed only when the amount of change in the parasitic capacitance Cp of the electrode is large and the variation in the parasitic capacitance Cp of the electrode is not large. Therefore, calibration is performed when the parasitic capacitance Cp of the electrodes has changed overall due to changes over time, etc., while calibration can be prevented from being performed when the parasitic capacitance Cp has changed significantly in part as shown at D2 in Fig. 5c due to the smartphone 4 being irregularly placed in front of the touch panel 11 as shown in Fig. 5b. Therefore, calibration is performed only under circumstances where it is truly appropriate to perform it.

[0035] Note that by not calibrating the distribution of the parasitic capacitance Cp of D2 in Figure 5c in this way, touches cannot be detected correctly in the area of ​​the touch panel 11 on the back side of the smartphone 4, but this does not cause any problems because this area is blocked from user access by the smartphone 4 and is not touched. In addition to situations where the smartphone 4 is placed, events in which the Cp value changes non-constantly can also occur, for example, when the user's palm is touching the touch panel 11 when the calibration control process is being executed. However, according to this embodiment, it is possible to prevent calibration from being executed inappropriately even in such cases.

[0036] As the variation index value calculated in step 606, various index values ​​can be used as long as they represent the magnitude of variation in the parasitic capacitance Cp of each electrode detected in step 602. For example, the difference between the maximum and minimum values ​​of the parasitic capacitance Cp of each electrode detected in step 602 can be used as the variation index value. Alternatively, the variance of the parasitic capacitance Cp of the electrode can also be used as the variation index value. Furthermore, instead of the electrode parasitic capacitance Cp, a moving average Mave of the electrode parasitic capacitance Cp may be used as shown in FIG. 7a for the X electrode group, or an average Pave of the electrode parasitic capacitance Cp for each region as shown in FIG. 7b for the X electrode group, and the difference or variance between the maximum and minimum values ​​of the moving average Mave or the average Pave for each region may be used as the variation index value.

[0037] In Figures 7a and 7b, Cpi represents the parasitic capacitance Cp of the i-th electrode in the X-direction, and Mavei and Pavei represent the moving average Mave of the i-th region in the X-direction and the average Pave for each region. Here, when using the moving average Mave or the average Pave for each region, the moving average Mave and the average Pave for each region are calculated for the X electrode group and the Y electrode group, respectively. By using the moving average Mave and the average Pave for each region in this way, it is possible to accurately detect spatially biased variations in the X and Y directions, such as the distribution D2 in Figure 5c, which occurs when a smartphone 4 is placed in front of the touch panel 11, and to avoid performing calibration.

[0038] Furthermore, by using the moving average Mave and the average Pave for each region in this manner, it is possible to distinguish between cases where the parasitic capacitance Cp of the electrodes increases locally at both ends of touch panel 11 that are easily touched due to the progress of moisture absorption, as shown in the X direction in Fig. 7c, and cases where the parasitic capacitance Cp of the electrodes is locally affected by impulse noise, and to identify a distribution in which the parasitic capacitance Cp increases with a spatial spread, such as D2 in Fig. 5c. Note that in Fig. 7c, the upper graph is a graph when the degree of moisture absorption is greater.

[0039] The first embodiment of the present invention has been described above. Next, a second embodiment of the present invention will be described. The second embodiment is intended for a case where there is design variation in the parasitic capacitance Cp of each electrode. Such design variations include variations in the parasitic capacitance Cp of each electrode due to the fact that at least a portion of the periphery of the touch panel 11 is surrounded by a ground pattern GP, ​​as shown in Figure 8a, or because the touch panel 11 is not rectangular and each electrode has a different size.

[0040] In the case of the touch panel 11 shown in FIG. 8a, as shown in FIG. 8b in the X direction, the electrodes near the ground pattern GP have a strong ground coupling and the parasitic capacitance Cp is large, and in the range where the size of the electrodes is small, the parasitic capacitance Cp is small. Therefore, in the second embodiment, before calculating the variation index value in the first embodiment, the parasitic capacitance Cp of each electrode is corrected so that the design variation is offset, and the variation index value of the parasitic capacitance Cp of each electrode after correction is calculated. Here, in this correction, for example, if the design variation is as shown in Fig. 8b, the parasitic capacitance Cp of each electrode is corrected so that the design variation is offset and the parasitic capacitance Cp becomes as shown in Fig. 8c.

[0041] Now, the procedure of the calibration control process for performing such correction is shown in FIG. As shown in the figure, in the calibration control process, the calibration controller 125 first detects the parasitic capacitance Cp of the electrode corresponding to each detection circuit 1211 from the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211 (step 902).

[0042] Then, the change in the parasitic capacitance Cp from the value detected in the previous calibration control process is calculated for each electrode, and it is checked whether the total of the calculated changes is greater than a predetermined threshold value Th1 (step 904).If it is not greater, the calibration control process is terminated.

[0043] On the other hand, if the total of the calculated amounts of change is greater than the threshold value Th1, the detected parasitic capacitance Cp of each electrode is corrected so as to cancel out the design variations (step 906). Then, a variation index value indicating the magnitude of variation in the electrode parasitic capacitance Cp after correction is calculated, and it is checked whether the variation index value is greater than a predetermined threshold value Th2 (step 908). If it is greater, the calibration control process is terminated. On the other hand, if the variation index value is not greater than the value Th2, the above-described calibration is performed for each detection circuit 1211 (step 910), and the calibration control process ends. The second embodiment has been described above. Next, a third embodiment of the present invention will be described. The third embodiment is intended to cancel an erroneous calibration that has been performed due to a human body touching the touch panel 11 or a conductive object near the touch panel 11 during the calibration process.

[0044] The procedure for the calibration control process for performing such cancellation is shown in FIG. As shown in the figure, in the calibration control process, the calibration controller 125 first detects the parasitic capacitance Cp of the electrode corresponding to each detection circuit 1211 from the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211 (step 1002).

[0045] Then, the change in the parasitic capacitance Cp from the value detected in the previous calibration control process is calculated for each electrode, and it is checked whether the sum of the calculated changes is greater than a predetermined threshold value Th1 (step 1004).If it is not greater, the calibration control process is terminated.

[0046] On the other hand, if the total amount of change is greater than the threshold value Th1, a variation index value indicating the magnitude of variation in the parasitic capacitance Cp of the detected electrode is calculated, and it is checked whether the variation index value is greater than a predetermined threshold value Th2 (step 1006).If it is greater, the calibration control process is terminated. On the other hand, if the variation index value is not greater than the value Th2, the above-described calibration is performed for each detection circuit 1211 (step 1008). Next, once the calibration is completed, the latest parasitic capacitance Cp of the electrode corresponding to each detection circuit 1211 is detected again from the RAW data stored in the memory 123 by the digitizer 121110 of each detection circuit 1211 (step 1010). Then, a variation index value indicating the magnitude of variation in the detected electrode parasitic capacitance Cp is calculated again, and it is checked whether the variation index value is greater than a predetermined threshold value Th2 (step 1012). If it is not greater, the calibration control process is terminated. On the other hand, if the variation index value is greater than the predetermined threshold value Th2, the calibration is canceled (step 1014) by restoring the state of each detection circuit 1211 to the state before the calibration was performed in step 1008, and the calibration control process ends. More specifically, in step 1014, the time t for which the third switch 12116 of each detection circuit 1211 is turned on is restored to the time t before the calibration was performed in step 1008.

[0047] In the calibration control process of the third embodiment, similarly to the second embodiment, before calculating the variation index value in steps 1006 and 1012, the parasitic capacitance Cp of each electrode may be corrected so that the design variation is offset, and the variation index value of the parasitic capacitance Cp of each electrode after correction may be calculated.

[0048] The embodiments of the present invention have been described above. In the above embodiment, calibration is performed by adjusting the time t for turning on the third switch 12116 of the detection circuit 1211 shown in Fig. 3, but this calibration may also be performed by adjusting the specifications of other elements of the detection circuit 1211 (for example, the value of the constant current of the constant current circuit 12115 or the attenuation rate of the attenuator 12117). Also, the detection circuit 1211 may have a configuration different from that shown in Fig. 3.

[0049] Furthermore, although the above description has been given taking an example of application to a self-capacitance touch panel 11, this embodiment can also be applied to a mutual-capacitance touch panel 11 in the same manner. In other words, in this case, calibration should be performed only when the amount of change in the mutual capacitance between the Y electrode and the X electrode when not touched, which is the base capacitance in the mutual capacitance formula, is large and the variation in the base capacitance is not large. [Explanation of symbols]

[0050] 1...touch panel unit, 2...host device, 3...peripheral device, 4...smartphone, 11...touch panel, 12...touch detection device, 121...sense block, 122...scan control unit, 123...memory, 124...data processing unit, 125...calibration controller, 1211...detection circuit, 12111...sequence controller, 12112...charging circuit, 12113...first switch, 12114...second switch, 12115...constant current circuit, 12116...third switch, 12117...attenuator, 12118...capacitor, 12119...fourth switch, 121110...digitizer.

Claims

1. A touch detection device used to detect a touch on a capacitive touch panel, a touch detection unit that detects capacitance of each of a plurality of points on the touch panel; a calibration unit that performs calibration for adjusting a range in which the touch detection unit detects the capacitance for each point; the calibration unit acquires the capacitances of the plurality of points detected by the touch detection unit at a predetermined trigger, and, if a change level representing the level of change in the capacitance of each acquired point relative to the capacitance at the time of the previous calibration is greater than a predetermined level and an index value representing the degree of variation in the capacitance of each acquired point is smaller than a predetermined value, performs calibration to adjust the range in which the touch detection unit detects the capacitance for each point based on the capacitance acquired for that point so as to include the capacitance of that point both when untouched and when touched.

2. 2. The touch detection device according to claim 1, The touch detection device according to claim 1, wherein the calibration unit uses, as the change level, a sum of the amounts of change in the capacitance of each acquired point relative to the capacitance at the time of the previous calibration.

3. 2. The touch detection device according to claim 1, The touch detection device is characterized in that the calibration unit uses the difference between the maximum and minimum values ​​of the capacitance of each acquired point as the index value.

4. 2. The touch detection device according to claim 1, A touch detection device characterized in that the calibration unit uses as the index value the difference between the maximum and minimum values ​​of the moving average of two or more points of the capacitance of each acquired point, with one direction on the touch panel as the movement direction.

5. 2. The touch detection device according to claim 1, A touch detection device characterized in that the calibration unit uses the difference between the average maximum and minimum values ​​of the capacitance of each acquired point for each of multiple areas into which the touch panel is divided in at least one direction as the index value.

6. 2. The touch detection device according to claim 1, The touch detection device is characterized in that, during the calibration, the calibration unit adjusts a range in which the touch detection unit detects the capacitance for each point to a range centered on the capacitance acquired for that point.

7. 2. The touch detection device according to claim 1, The calibration unit corrects the capacitance of each acquired point so that the design capacitance variation is at least partially offset, and calculates a value representing the degree of variation in the corrected capacitance of each point as the index value.

8. 2. The touch detection device according to claim 1, the calibration unit acquires the capacitances of the plurality of points detected by the touch detection unit after performing the calibration, and if an index value representing the degree of variation in capacitance of each acquired point is greater than the predetermined value, restores the range in which the touch detection unit detects the capacitance for each point to the range before performing the calibration.

9. 2. The touch detection device according to claim 1, The touch detection device, wherein the predetermined trigger is activation of the touch detection device.

10. 10. A touch detection device according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, the touch panel is a self-capacitance touch panel having a plurality of X electrodes and a plurality of Y electrodes; A touch detection device, wherein each X electrode and each Y electrode are the points at which the touch detection unit detects capacitance.

11. A touch panel device comprising: the touch detection device according to claim 1; and the capacitance type touch panel.

12. A touch panel device comprising: the touch detection device according to claim 10; and the self-capacitance touch panel.

13. 1. A calibration method for calibrating a touch detection device used to detect touches on a capacitive touch panel, comprising: the touch detection device includes a touch detection unit that detects capacitance of each of a plurality of points on the touch panel, and a calibration unit; The calibration method includes: a first step of acquiring capacitances of the plurality of points detected by the touch detection unit at a predetermined opportunity in the calibration unit; and performing a calibration step in which, when a change level representing a level of change in the capacitance of each point acquired in the first step relative to the capacitance at the time of the previous calibration is greater than a predetermined level and an index value representing a degree of variation in the capacitance of each acquired point is smaller than a predetermined value, the calibration step adjusts a range in which the touch detection unit detects the capacitance for each point based on the capacitance acquired for that point so as to include the capacitance of that point both when untouched and when touched.

14. The method for calibrating a touch detection device according to claim 13, the touch panel is a self-capacitance touch panel having a plurality of X electrodes and a plurality of Y electrodes; A calibration method for a touch detection device, wherein each X electrode and each Y electrode are the points at which the touch detection unit detects capacitance.

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